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perf hist: Clarify events_stats fields usage

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The events_stats.total field is too generic, rename it to .total_period,
and also add a comment explaining that it is the sum of all the .period
fields in samples, that is needed because we use auto-freq to avoid
sampling artifacts.

Ditto for events_stats.lost, that is the sum of all lost_event.lost
fields, i.e. the number of events the kernel dropped.

Looking at the users, builtin-sched.c can make use of these fields and
stop doing it again.

Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo
2010-05-14 13:16:55 -03:00
parent c8446b9bda
commit cee75ac7ec
9 changed files with 41 additions and 34 deletions
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16
tools/perf/util/hist.h
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@@ -37,9 +37,21 @@ struct sym_priv {
struct sym_ext *ext;
};
/*
* The kernel collects the number of events it couldn't send in a stretch and
* when possible sends this number in a PERF_RECORD_LOST event. The number of
* such "chunks" of lost events is stored in .nr_events[PERF_EVENT_LOST] while
* total_lost tells exactly how many events the kernel in fact lost, i.e. it is
* the sum of all struct lost_event.lost fields reported.
*
* The total_period is needed because by default auto-freq is used, so
* multipling nr_events[PERF_EVENT_SAMPLE] by a frequency isn't possible to get
* the total number of low level events, it is necessary to to sum all struct
* sample_event.period and stash the result in total_period.
*/
struct events_stats {
u64 total;
u64 lost;
u64 total_period;
u64 total_lost;
u32 nr_events[PERF_RECORD_HEADER_MAX];
u32 nr_unknown_events;
};